1. Field of the Invention
The present invention relates to an ink jet recording sheet forming an ink receiving layer on a base material, and more particularly to an ink jet recording sheet excellent in fading preventive effect when printed in an oil-based ink.
2. Description of the Related Art
As one of printing methods, the ink jet recording method is rapidly expanding its application owing to its advantages such as reproduction of full-color image of high picture quality and low running cost. In the ink jet recording method, hitherto, water-based ink has been used, but recently oil-based ink is used more increasingly. The water-based ink is an ink of which solvent is water or a solvent having a high affinity for water, and the oil-based ink is an ink of which solvent is mainly a petroleum high boiling point solvent. The oil-based ink is used more increasingly because it is noticed that the printed image has a higher weather resistance.
Incidentally, when the oil-based ink is printed on an ink jet recording sheet suited to the conventional water-based ink, the absorption of ink solvent is inferior, and flow of image and other problems occur. Therefore, the ink jet recording sheet is required to have a high applicability to the oil-based ink.
Various materials have been proposed so far as ink jet recording sheets suitable to the oil-based ink. For example, Japanese Laid-open Patent No. 11-165460 proposes an invention of an ink jet recording sheet forming an intermediate layer and an ink receiving layer on a base material, in which the intermediate layer contains a resin which dissolves or swells in a petroleum high boiling point solvent.
The recording sheet proposed by this invention is an excellent ink jet recording sheet for the oil-based ink because the intermediate layer absorbs the solvent of the oil-based ink. However, recently, as the requirements for image are diversified as a result of expansion of application of ink jet recording system, even in the case of using the oil-based ink, there is an increasing demand for ink jet recording sheet less in fading after lapse of time, in addition to the image quality right after printing. This demand cannot be sufficiently satisfied by the conventional ink jet recording sheet for the oil-based ink.
In the light of the problems of the conventional ink jet recording sheet for the oil-based ink, it is an object of the invention to present an ink jet recording sheet excellent not only in the image quality right after printing, but also in fading preventive effect when printed in the oil-based ink.
To solve the problems, the invention presents an ink jet recording sheet forming an ink receiving layer on a base material, in which the ink receiving layer contains at least one of chlorinated polypropylene, compound of chlorinated polypropylene, versatic acid vinyl ester, and compound of versatic acid vinyl ester.
In the configuration of the invention, preferably, the ink receiving layer may contain a resin which does not dissolve or swell in a petroleum high boiling point solvent in an oil-based ink. Preferably, an intermediate layer containing a resin capable of absorbing and holding a petroleum high boiling point solvent in an oil-based ink may be provided between the ink receiving layer and the base material, and such resin is a resin which swells in the solvent, or swells and then dissolves therein.
Explaining the point of notice by the inventor of the present invention, the present inventor intensively studied, and discovered that an excellent fading preventive effect is obtained by containing the following substances in the ink receiving layer, in the ink jet recording sheet forming a porous ink receiving layer on a base material. That is, such substance is one of chlorinated polypropylene, compound of chlorinated polypropylene, versatic acid vinyl ester, and compound of versatic acid vinyl ester. The reasons of exhibiting the fading preventive effect are estimated as follows. First, these substances are excellent in performance of fixing coloring material in the ink. Therefore, after printing, it is expected to suppress the phenomenon of the coloring material in the ink sinking in the direction of the base material. Second, these substances are very large in the property of swelling in the petroleum high boiling point solvent or swelling and dissolving therein. Accordingly, when printed, these substances are swell or dissolve in the petroleum high boiling point solvent in the ink, and the pores in the ink receiving layer are filled up, thereby suppressing passing and sinking of the coloring material in the ink through pores.
Embodiments of ink jet recording sheet of the invention are explained.
The recording sheet of the invention is composed of an ink receiving layer formed on a base material as described below, and further an intermediate layer may be provided between the base material and ink receiving layer.
The ink receiving layer of the invention contains at least one of chlorinated polypropylene, compound of chlorinated polypropylene, versatic acid vinyl ester, and compound of versatic acid vinyl ester. Among these substances, denatured chlorinated polypropylene and vinyl acetate-ethylene-versatic acid vinyl ester copolymer are preferably used in particular. The content of these substances is preferred to be 3 to 30 wt. % of the total solid content weight of the ink receiving layer. If less than 3 wt. %, fading preventive effect is insufficient, or if exceeding 30 wt. %, the strength of the printed portion of the ink receiving layer is insufficient. More preferably, the content is 5 to 25 wt. %.
In the ink receiving layer, aside from the above substances, it is preferred to contain a filler. As the filler, various known inorganic fillers and organic fillers can be used. Inorganic fillers include silica, calcium carbonate, diatom earth, and kaolin. Organic fillers include styrene and methacrylic acid beads. In particular, inorganic fillers are preferred, and silica is most suitable from the viewpoint of ink absorption.
The ink receiving layer may contain, aside from at least one of chlorinated polypropylene, compound of chlorinated polypropylene, versatic acid vinyl ester, and compound of versatic acid vinyl ester, and the filler, various known binders. As the binder, it is preferred to use a resin which does not dissolve or swell in the petroleum high boiling point solvent. When a resin which does not dissolve or swell in the petroleum high boiling point solvent is contained, the strength is increased in the printed portion of the ink receiving layer when printed in an oil-based ink. Examples of resin which does not dissolve or swell in the petroleum high boiling point solvent may be selected from ester acrylate copolymer resins and polyvinyl alcohols. In the ink receiving layer, the blending ratio of at least one of chlorinated polypropylene, compound of chlorinated polypropylene, versatic acid vinyl ester, and compound of versatic acid vinyl ester to the resin which does not dissolve or swell in the petroleum high boiling point solvent should be in a range of 7:3 to 1:9. In this range, both the fading preventive effect and the strength of the ink receiving layer are likely to be satisfied at the same time.
The ink receiving layer may also contain various additives as required, such as surface active agent, antistatic agent, and ultraviolet ray absorbent. The thickness of the ink receiving layer is preferably 10 to 60 xcexcm. More preferably, it is 20 to 50 xcexcm. The ink receiving layer can be formed on the base material by coating, spraying, immersing, etc. In the coating process, various known devices can be used, such as air knife coater, bar coater, and roll coater.
In the invention, an intermediate layer may be provided between the ink receiving layer and the base material. In particular, it is preferred to place an intermediate layer containing a resin which swells in the petroleum high boiling point solvent, or swells and then dissolves therein. By inserting such intermediate layer, the ink absorption of the enter ink jet recording sheet is enhanced when printed in an oil-based ink, and fixing of coloring material in the ink receiving layer is stronger. As a result, together with the effects of the ink receiving layer of the invention, an ink jet recording sheet particularly excellent in suitability to the oil-based ink is realized.
The intermediate layer is mainly composed of a binder resin, and further silica, titanium oxide or other filler may be added in order to enhance the blocking preventive property or opacity. The binder resin mainly composing the intermediate layer is preferred to be capable of absorbing and holding the petroleum high boiling point solvent used as the solvent for oil-based ink, and hence it is preferred to have a property of swelling in the petroleum high boiling point solvent, or swelling and then dissolving in the petroleum high boiling point solvent. The binder having such property, after being formed as the intermediate layer, only swells but does not dissolve in the amount of ink used in the ink jet recording condition. As such resin, for example, styrene resin and rubber resin may be used, and styrene resin alone, rubber resin alone, or their mixture at a proper rate may be used. The resins to be contained in the intermediate layer may include, aside from such styrene resin and rubber resin, acrylic resin, polyester resin, and urethane resin.
Examples of styrene resin include styrenic alkyd resin, styrene-acrylic copolymer resin, and their substituent derivatives. Substituent derivatives are, for example, carboxylated one and its alkaline reactive one.
Examples of rubber resin include styrene-butadiene copolymer resin, ester methacrylate-butadiene copolymer resin, urethane acrylate rubber, polynorbonene resin, and their substituent derivatives. Substituent derivatives are, for example, carboxylated one and its alkaline reactive one.
One or plural types of styrene resin and rubber resin may be mixed. Among the resins, in particular, styrene-butadiene copolymer resin and polynorbonene resin show excellent solubility in the petroleum high boiling point solvent, and exhibit a smooth swelling property in the solvent as intermediate layer. As the petroleum high boiling point solvent as the solvent for an oil-based ink, isoparaffin and paraffin are preferably used.
The thickness of the intermediate layer is about 1 to 10 xcexcm, and more preferably about 2 to 8 xcexcm, but the thickness may be properly adjusted in relation to the type of ink solvent and ink absorbing amount. Herein, the intermediate layer is composed of one layer only, but may be also composed of two or more layers by using one or two or more different resins selected from styrene resins and rubber resins.
The base material of the invention is not particularly specified, and plastic films, paper, synthetic paper, nonwoven cloth and others may be used. In particular, plastic films are preferred from the viewpoint of resistance to water. Specific examples are general thermoplastic resin films such as polyethylene terephthalate, polypropylene, polystyrene, or polycarbonate, or those incorporating inorganic powder such as calcium carbonate, incorporating organic pigment, or forming voids in manufacturing process, white polyester film with glossy surface incorporating titanium oxide, transparent polypropylene film, and other light permeable plastic films. The thickness of the base material may be properly selected depending on the purpose, and usually it is about 50 to 250 xcexcm. Or, to improve adhesion to the intermediate layer, or adhesion to the ink receiving layer if intermediate layer is not provided, the surface of the base material may be processed by anchor coating or corona discharge.